@inproceedings{SIGMOD-1983-MaierU,
	author        = "David Maier and Jeffrey D. Ullman",
	booktitle     = "{Proceedings of the 13th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD83/P015.PDF",
	doi           = "10.1145/582192.582200",
	pages         = "15--22",
	publisher     = "{ACM Press}",
	title         = "{Fragments of Relations}",
	year          = 1983,
}